After-effects of ceftriaxone/tazobactam on Escherichia coli producing extended-spectrum β-lactamases
OBJECTIVE To determine the minimal inhibitory concentration(MIC),post-antibiotic effect(PAE)and post β-lactamase inhibitor effect(PLIE)of ceftriaxone/tazobactam against extended-spectrum β-lactamase-producing Escherichia coli(ESBLs-Eco).METHODS MIC was gauged by broth microdilution method.Colony forming unit was determined by colony counting method.Bacterial growth curve was plotted with culture time as abscissa and logarithm of colony number as ordinate and PAE/PLIE calculated.RESULTS As compared with ceftriaxone alone,MIC of ceftriaxone/tazobactam to ESBLs-Eco was sig-nificantly lower.And PAE and PLIE of ceftriaxone/tazobactam to ESBLs-Eco were negative or shorter at lower drug concentra-tions.When after-effect was positive,PLIE＞PAE.And PAE and PLIE of ceftriaxone/tazobactam to ESBLs-Eco were pro-longed with rising drug concentrations.At a concentration of ceftriaxone/tazobactam 800×MIC,PAE was 3.65 h and PAE＞12.86 h.CONCLUSION Ceftriaxone/tazobactam has a concentration-dependent effect on PAE/PLIE of ESBLs-Eco.And PAE/PLIE play some important roles in maintaining the lasting in vivo antibacterial activity of ceftriaxone/tazobactam.And the potency of PLIE is stronger than that of PAE.
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